This invention relates to glass-ceramics capable of being used broadly for various precision parts which require an ultra low thermal expansion property, super surface flatness or a high rigidity and being particularly suitable for use as various parts of next generation semiconductor equipment.
In the present specification, the term “difference between the maximum value and the minimum value of ΔL/L” means difference in a temperature range from 0° C. to a given temperature between the maximum value and the minimum value of ΔL/L where L represents length of a piece of a glass-ceramic at 0° C. and ΔL represents amount of change in the length of the glass-ceramic at the given temperature.
In the present specification, the term “ultra low thermal expansion property” means a property of a glass-ceramic which has an average linear thermal expansion coefficient within a range of 0.0±0.2×10−7/° C., preferably 0.0±0.1×10−7/° C. within a temperature range from 0° C. to 50° C. and has difference between the maximum value and the minimum value of ΔL/L of 10×10−7 or below, preferably 8×10−7 or below.
In the present specification, “predominant crystal phase” means all crystal phases which have a relatively large ratio of precipitation. More specifically, “predominant crystal phase” includes all crystal phases each of which, when X-ray diffraction intensity of a main peak (the highest peak) of a crystal phase which has the largest ratio of precipitation in an X-ray chart of X-ray diffraction (the vertical axis representing X-ray diffraction intensity and the horizontal axis representing diffraction angle) is assumed to be 100, has a main peak (the highest peak in the crystal phase) whose ratio of X-ray diffraction intensity (hereinafter referred to as “X-ray diffraction intensity ratio”) is 30 or over. X-ray diffraction intensity ratios of crystal phases other than the predominant crystal phases should preferably be less than 20 and, more preferably less than 10 and most preferably, less than 5.
In recent technology of lithography, development of a higher density integration in a semiconductor circuit enhances an active development for reducing width of exposure line. For example, as a next generation technology, development of technology using KrF laser beam with a wavelength of 0.248 μm or ArF laser beam with a wavelength of 0.193 μm has been actively made in the optical type lithography. Further, for realizing a smaller semiconductor circuit, there have been made a development of a variable wavelength system using EPL (electron projection lithography) and a development of EUV (extreme ultraviolet) system using extreme ultraviolet ray having wavelength of 0.0134 μm.
Component parts used for such next generation lithography technology for the manufacture of semiconductors are required to have thermal stability in size, strength, thermal durability and chemical stability, particularly an ultra low thermal expansion property which is necessary for thermal stability in size.
As component parts of the prior art semiconductor equipment, Si and SiO2 materials have been used. The Si material is a high thermal expansion material with an average linear thermal expansion coefficient α of 30×10−7/° C. and the SiO2 material which is of a relatively low thermal expansion property still has α of 5×10−7/° C. which is far from being satisfactory for the ultra low thermal expansion property required for a high precision design and, therefore, has difficulty in application for the next generation lithography.
As materials for eliminating the defects of these materials, general transparent glass-ceramics and SiO2—TiO2 glasses manufactured by CVD (chemical vapor deposition) may be considered. The material manufactured by CVD, however, is not free from defects in the form of cords produced in one direction by stacking of the material with the result that the average linear thermal expansion coefficient of the material obtained has anisotropy and, therefore, is not satisfactory in thermal stability in size.
Aside from the quartz glass and the SiO2— TiO2 glass, known in the field of general transparent glass-ceramics is a SiO2—Al2O3—Li2O transparent glass-ceramic which has realized various low thermal expansion characteristics. For example, Japanese Patent Publication 77137/1991 and U.S. Pat. No. 4,851,372 disclose glass-ceramics which comprise TiO2 and ZrO2 as nucleating agents and additionally comprise P2O5, MgO, CaO, Na2O and K2O as optional ingredients. These glass-ceramics, however, have a large average linear thermal expansion coefficient of 1×10−7/° C. and the highly accurate ultra low thermal expansion property which is the object of the present invention is not considered in these publications at all.
Japanese Patent No. 2668057 discloses glass-ceramics which comprise TiO2 and ZrO2 as nucleating agents. These glass-ceramics also have a broad range of average linear thermal expansion coefficient of 0±5×10−7/° C. and the highly accurate ultra low thermal expansion property which is the object of the present invention is not considered in this publication at all.
Various parts used in the lithography technology for the next generation semiconductor equipment are required to have the following properties for reduction in the width of the exposure line of the integrated circuit and also for higher accuracy of the integrated circuit:    (1) The parts should have an ultra low thermal expansion property.    (2) The parts should have a super flat surface roughness after polishing.    (3) For realizing the flatness, the average crystal grain diameter of the material should be very small.    (4) Influences by heat and vibration should be minimum.    (5) The parts should be free of Na2O and K2O ingredients which tend to cause contamination of the materials of the parts in the film forming and rinsing processes.
It is, therefore, an object of the present invention to provide glass-ceramics which have eliminated the above described defects of the prior art materials and have realized the ultra low thermal expansion property and super flat surface capable of coping with lithography for the next generation LSI.
It is another object of the invention to provide component parts for semiconductor equipment such as masks, optical reflecting mirrors, wafer stages and reticle stages and various precision parts.